Dielectric materials with low dielectric constant (k) are used in making the interconnect structure of integrated circuits (IC), and new materials with improved properties are the focus of much current research. In addition to having a low dielectric constant, to be useful in electronic devices, the materials must also be thermally and chemically stable; mechanically robust; free of corrosives or mobile charges; and compatible with current IC manufacturing processes. It is especially desirable to be able to form a layer of dielectric material via spin-coating. Additional requirements may include strong adhesion to other component or layers of an IC and low shrinkage.
One promising class of materials is highly crosslinked organosiloxanes. These materials are prepared by the platinum-catalyzed crosslinking of polyhydrosiloxanes with polyvinylsiloxanes. The material derived from D4Vi (tetramethyltetravinylcyclotetrasiloxane) and D4H (tetramethylcyclotetrasiloxane) is a “hard, glassy material”, with excellent thermal stability up to 450° C. Both siloxanes are low viscosity liquids and thus solvents are not required to form liquid mixtures. Also, the hydrosilation reaction proceeds smoothly and with high conversion at very low platinum concentration. (See M. J. Michalczyk et al., Chemistry of Materials, Vol. 5 (12), 1993, pp 1687-1689; and S. U. A. Redondo et al., Polymer 42 (2001) 1319-1327.)
JP 2005298606 discloses a process for preparing heat-resistant curable cyclosiloxane compositions by heating a mixture of two different siloxane polymers and a hydrosilation catalyst. In one example, a composition comprising a 6:1 reaction product of 1,3,5,7-tetramethylcyclotetrasiloxane (I) and 1,3,5,7-tetravinyl-1,3,5,7-tetramethylcyclotetrasiloxane (II), a 1:6 reaction product of (I) and (II), and a Pt-vinyltetramethyldisiloxane complex was applied on an Al board and heated at 150° C. for 2 hr to give a coating that reportedly has good adhesion and no surface cracks.
There is a continuing need for dielectric materials that have suitably low k properties, are thermally and mechanically robust, and can be prepared by processes that are compatible with current IC fabrication steps.